package com.zzy.singleton.singleton2;

/**
 * 懒汉式
 * 线程安全 延迟加载 效率较高
 */
public class SingletonTest2 {
    public static void main(String[] args) {
        Singleton instance1 = Singleton.getInstance();
        Singleton instance2 = Singleton.getInstance();
        System.out.println(instance1 == instance2);
        System.out.println("instance1.hashCode()>>>" + instance1.hashCode());
        System.out.println("instance2.hashCode()>>>" + instance2.hashCode());
    }
}

class Singleton {

    private static volatile Singleton instance;

    private Singleton() {
    }

    public static Singleton getInstance() {
        if (instance == null) {
            synchronized (Singleton.class) {
                if (instance == null) {
                    instance = new Singleton();
                }
            }
        }

        return instance;
    }
}